Possible CCU issue?

Robin_Cox

Member
Hello again,

After a month of untroubled driving, a couple of minor gremlins and some error codes have been thrown up that I thought the combined brains trust will probably be able to interpret rather better than I can.

2004 Tdi 75 ; I realised on picking it up that the battery was tired, and it appears to have been the original one when I got it replaced with a large Bosch that resolved the weak cranking. I've been told anecdotally this can cause some false positive errors in various systems unless one clears the fault codes (which I haven't yet done).

Last night the climate control was set on a gentle 20 (with Econ engaged) on a 20 minute drive home. As the car was beginning to mist up I turned off Econ. The windows cleared ; however after a few minutes of town driving and getting onto the dual carriageway I realised that the car was getting hotter and hotter - basically the same as when my A6 climate is set on HI. I put Econ back on, and the temperature still continued to rise, even with the temp setting turned down to LO. This continued for the next few minutes until we got home (by this time with the windows open as we were reaching sauna point!). Today - climate completely back to normal. I've gathered from various threads this could have been a stuck / confused flap rather than anything to do with CCU. I do have an open circuit code on the coolant sensor (and the temp gauge has only worked the first time I drove it) which is the next scheduled DIY fix along with thermostat.

This afternoon, got into the car and the 'drivers door open' diagram remained on the screen, and the internal lights stayed on. Microswitch was my first thought, but then I remembered that now and again when I put the key in the ignition before starting the door locks trigger on and off a couple of times and various threads saying this was a symptom of a deteriorating CCU. This stayed the same until I got home when I put the ODB reader in and scanned the CCU.

Faults -
01616 (signal wire to internal monitor sporadic [I had to replace the doorframe switch a month ago as it had failed])
01562 right rear door no unlock (it does)
01366 crash signal sporadic open circuit
01403 glass break sensor rear sporadic open circuit
01560 passenger door sporadic does not unlock (now and again)

The CCU in question is an 8Z0 959433 AF.

I've just gone and unlocked the car again, and the drivers door open signal has gone while the internal lights go out as expected.

Any thoughts? It is more a ghost in the machine than something terminally inconvenient right now (could some of the above be legacy of the dud battery?), but opinions on whether getting a refurbed CCU or a second-hand AF would be a good idea in due course would be appreciated.

Many thanks.
 
It doesn’t sound like the cccu at fault. But the driver’s door microswitch seems to be playing up (confirmed by the door not registering as shut on that occasion and the locks cycling when you turn the ignition on)

i would recomend clearing the errors and re scanning. They are typical of a flat battery or one that went to zero when cranking.

Steve B
 
from my experience of the A2 I don't think it is the CCCU at fault
I would start with the drivers door lock SOLDER Joint, I have had this problem with lock cycling and interior light not working on all of my A2's and in ALL cases it was the solder joints that had cracked. Re flowing the joints with leaded solder ans some flux with a good hot soldering iron as fixed the problems once and for all.

The route of the problem is the lead free solder that was used, it was the early days for lead free solder and the results are a brittle joint, combine this with a mix of thinner and much thicker wires/terminals to solder to the circuit board and stress put on the joints via the wiring loom and you have the classic causes for fractured solder joints
BTW lead free solder is still crap compared to leaded solder, the the former is considered more environmentally friendly (even though it does not do the job half as well as leaded solder)

I like to head the original joint with some liquid flux applied and use a solder sucker to remove as much as possible of the lead free crap, then apply a little more flux and re make the solder joint with proper leaded solder, the resultant joint is bright and sparkly and will withstand the flexing FAR better as lead is very malleable as against lead free which is very brittle

Cheers,
 
Why on ECON? My understanding is that if one wants one’s climate control to function troublefree, one needs to use it.
The only time I use ECON is on a cold, clear day with OpenSky open, and the heater on.
Andrew
 
Why on ECON? My understanding is that if one wants one’s climate control to function troublefree, one needs to use it.
The only time I use ECON is on a cold, clear day with OpenSky open, and the heater on.
Andrew

Yes, I don't think I have ever used ECON, I either have air con on all year or switch it off when the OSS is open.

Steve B
 
Econ simply because of being habitually miserly.. to be honest (after 2 tank fills of everyday driving) the car is doing an easy 56.5mpg exclusively on short commutes and shopping trips even with a dicky coolant sensor and potential thermostat issue, so using Econ is probably having no positive effect on the fuel economy at all. Driving the car up from London in September it went 530 miles on 37 litres of fuel (so should have easily done ~600 miles on the tank had I run it to the dregs). Thanks again for the suggestions re the door microswitch and re-doing the solder - I've already re-soldered the notorious connection in the rear reading light that was cracked and not working when the doors opened. It may be a small fix, but the sense of satisfaction seeing the light return to normal function having found the repair solution here was enormous.
 
My understanding is that if one wants one’s climate control to function troublefree, one needs to use it.

You cannot switch it off completely because there is no way of completely switching off the compressor, unless the drive fails. Therefore refrigerant is always circulating in the system, to a greater or lesser degree. The idea that you have to run the A/C to maintain the seals is not true. If contact between the seals and refrigerant affected the seals in any way, physically or chemically, the seals would be considered as being incompatible. The seal compound is chosen for its' compatibility. So if you want to switch A/C "off", do so. It won't make any difference to its' serviceability.

RAB
 
Hi Robin,

It sounds like your A2 has multiple simultaneous minor issues rather than one.

Just to clarify some acronyms to avoid confusion...
The CCCU (frequently abbreviated to just CCU on this forum) is the Central Convenience Control Unit. It is one of the car's main brains and lives under the passenger's feet. Some people assume that it's an abbreviation of Climate Control Unit, but the Climate Control Unit and the Central Convenience Control Unit are two totally separate pieces of equipment. My apologies if you were well aware of this.

Last night the climate control was set on a gentle 20 (with Econ engaged) on a 20 minute drive home. As the car was beginning to mist up I turned off Econ. The windows cleared ; however after a few minutes of town driving and getting onto the dual carriageway I realised that the car was getting hotter and hotter - basically the same as when my A6 climate is set on HI. I put Econ back on, and the temperature still continued to rise, even with the temp setting turned down to LO. This continued for the next few minutes until we got home (by this time with the windows open as we were reaching sauna point!). Today - climate completely back to normal. I've gathered from various threads this could have been a stuck / confused flap rather than anything to do with CCU.

Yep, this sounds like a stuck temperature flap. That'll be a fault with the climate control system, and nothing to do with the CCCU.

I do have an open circuit code on the coolant sensor (and the temp gauge has only worked the first time I drove it) which is the next scheduled DIY fix along with thermostat.

The coolant temperature sensor feeds a signal to the engine management unit and to the instrument cluster. It has no connection to either the climate control unit nor the CCCU.

This afternoon, got into the car and the 'drivers door open' diagram remained on the screen, and the internal lights stayed on. Microswitch was my first thought, but then I remembered that now and again when I put the key in the ignition before starting the door locks trigger on and off a couple of times and various threads saying this was a symptom of a deteriorating CCU. This stayed the same until I got home when I put the ODB reader in and scanned the CCU.

Both the issues you describe here (the 'door open' symbol and the cycling of the locks when turning the key in the ignition) are symptoms of a fault within one or more of the door locks. As Paul (Depronman) describes above, it's to do with a cracked solder joint on the door lock circuit board. The door locks feed their status signal to the CCCU (which in turn informs the instrument cluster display of which doors are open), but the CCCU is again blameless for the issues.

Cheers,

Tom
 
Thanks again for the detailed and comprehensive response. I had already worked out there is a difference between the CCU & CCCU after reading a lot of posts/threads here and noting the occasional terminology confusion but it is good to have it spelled out completely. It's not just me that'll be learning from this reply.

The consensus from all of you points at a specific soldered joint on one or more of the door lock circuit boards - I'm guessing if I read around a few of the threads on here or online about the microswitch fix I'll dig up a photo (non-Photobucket) of the joint in question much as with the rear seat light switch to be able to home in on the right one?

Have a great weekend everyone - I raise a beer in all of your directions! Good evening.
 
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